PowMeter Shield Nano

The powerful, tiny power monitor shield for your Arduino Nano

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Constantly and completely monitor your Arduino project’s power consumption with the PowMeter shield. This versatile solution replaces up to four multimeters with a ten gram device. (For french speaking people, there is a full presentation, here

Advantages of PowMeter Nano

  • A very small footprint. The shield attaches directly to your Nano, adding only 23 millimetres in length
  • Allows you to monitor USB voltage and current when powered through the USB port
  • Also allows you to monitor power consumption separately on a VIN MON pin
  • Peripheral power can be metered via the VAUX pin
  • It does not consume any of your project software resources, thanks to the onshield MCU
  • The shield draws less then 10 mA
  • All components communicate through I2C. This means you can take actions inside your own program depending on current or voltage values retrieved from the components
  • Good measurement precision
  • You can also use the onshield OLED for your own project
  • The OLED screen can be installed on either side of the board

Design Considerations

It’s always good practice to design a project with low energy usage in mind. But just using multimeters (and oscilloscopes) is tedious, error-prone, messy, and can even mess up your equipment. Something will go wrong almost every time. So I made PowMeter Nano to make measurement easy, compact, and something that you can integrate into your project.

I have always been interested by power consumption measurement, but the matter is harder than expected and I got bad measurements when I first started. I rapidly found that measuring a current on a rail that has higher or equal potential to the measurement circuit power is difficult, particularly if one looks for precise measurements. But after much research and after examining many IC options, my ultimate choice was the standard INA219 IC used by many Arduino makers. I chose it mainly because it would integrate into an “all I2C” architecture.

After the power measurement ICs were determined, I added an ATmega microcontroller and an OLED module to the PowMeter. All these are communicating through I2C. Measurement is done through 50 mOhms - 1% current sense resistors with a max of 1 W despite their small 1206 package footprint. This should prevent them from burning as easily as my multimeters calibers. Of course, short circuits should be avoided!

Specifications

  • USB Current measurement: 0 – 500 mA, can be modified up to 2A (short time), resolution 0.1 mA
  • VIN Current measurement: 0 – 4 A (continuous), 9.999 A (short time), resolution 0.5 mA
  • Current measurement error: less than 1% + (0.05 mA (USB), 0.25 mA (VIN))
  • Voltage band: 0 – 24 V, resolution 10 mV
  • Voltage measurement error: less than 1% + 0.01 V
  • Display resolution: 3 to 4 digits
  • Shield current draw: ~10 mA
  • High side or low side measurement: when used as a Nano Shield, measurement is on the high side
  • Dimensions: 66 mm * 18.2 mm * 18.5 mm
  • Weight: 10 grams

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